1. Field of the Invention
The present invention relates to an oscillation damper for a hand-held power tool and, in particular, a hammer drill, a combination hammer, or chisel hammer.
2. Description of the Prior Art
An oscillation damper represents an oscillation-capable sub-system that consists of an abstract oscillating mass, an abstract spring, and an abstract damper and that is not necessarily needed to be explicitly formed of concrete components. In particular, the abstract damper often is not formed by concrete components but nevertheless functions by using friction and flow losses which practically always present. There exist two types of dampers, conventional passive oscillation dampers that exclusively are self-excited, and actively controlled oscillation dampers.
By a suitable selection of spring constant and mass, in a passive damper, its natural frequency can be so dimensioned that it is closed to a to-be-damped interference frequency, in the present case, to the oscillations of the outer housing of the hand-held power tool.
French Publication FR 2,237,734 discloses use of a passive oscillation damper for preventing oscillation of a housing of a percussion hand-held power tool.
U.S. Pat. No. 4,478,293 discloses synchronization of operation of two passive oscillation dampers by using compressed air pulsation. Here, an abstract spring, which is formed as a helical spring, is oriented axially in the percussion direction of the power tool and is at least partially axially offset to a compact oscillating damping mass.
European Publication EP 1 710 052 discloses an arrangement of a hollow cylindrical passive oscillation damper around of a guide tube of a percussion mechanism.
International Publication WO 2006/022345 discloses an arrangement of a compact oscillation damper within the outer housing of a power tool on the housing side opposite the handle.
According to European Publication EP 1 415 768, an oscillation damper is located in a damper housing that is releasably form- or forcelockingly secured on remaining outer housing of the hand-held power tool, on a side surface of the housing remote from the handle and opposite thereto.
According to German Patent No. 815,179, two, compressively preloaded, helical springs are provided on opposite axial sides of a compact oscillating damping mass.
Because the total length of an oscillation damper is always greater than the spring length, for achieving a sufficient damping effect a relatively large, axially extending constructional space is required.
An object of the present invention is to reduce the total length of an oscillation damper suitable for being mounted in or on a hand-held power tool.